In commercial and industrial construction, installing or hanging duct systems is accomplished by installing all-thread rod from the structure and using steel supporting members as trapeze hangers. The size and length of the trapeze hanger is determined by the size and weight of the duct. Additionally, these trapeze hangers are subject to steel reinforcement requirements, such as those of SMACNA (Sheet Metal and Air Conditioning Contractors National Association, Inc.). Steel reinforcement of sheet metal ducts provides structural integrity on the all sides of the duct so that it can withstand the air pressure inside the duct. The type of reinforcement needed is determined by the type of material and size of the duct, as well as anticipated pressure to which the duct will be subjected. Reference can be made to SMACNA manuals for more specific charts and description of duct reinforcement.